Built in 1783 to defend against potential naval invasions and named for the mythical Mt Meru (Phra Sumen in Thai) of Hindu-Buddhist cosmology, the octagonal brick-and-stucco bunker was one of 14 city watchtowers that punctuated the old city wall alongside Khlong Rop Krung. Apart from Mahakan Fort, this is the only one still standing. Alongside the fort and fronting the river is a small, grassy park with an open-air pavilion, river views, cool breezes.